Hunterdon County Prosecutor Anthony Kearns III said authorities have learned witnesses may have observed the suspects, but did not remain in the area when authorities arrived.

"Anyone that witnessed any events prior, during, and after the armed robbery and has not formally spoken to the investigating agencies are urged to contact the Hunterdon County Prosecutor's Office," Kearns said in a statement today.

Kearns said witnesses may have seen the suspects fleeing from the store to the parking lot of the adjacent Liberty Village shopping center on Route 12. He said those witnesses may also have observed the vehicles used by the suspects to flee the robbery.

"Detectives are attempting to verify if there were additional suspects outside the store or if any additional vehicles were used by the suspects," Kearns said.

The five robbers ordered customers to the floor and bound some of the employees, while forcing other workers to open the jewelry showcase, police have said.

They then began stuffing diamond rings, necklaces, Rolex watches and other items into duffel bags, police said. They were in the store for about five minutes and left with hundreds of pieces of jewelry.

Anyone with information should contact the Hunterdon County Prosecutor's Office at 908-788-1129 or the Flemington Police Department at 908-782-3435.

Hunterdon County Crime Stoppers is offering a $1,000 reward for information leading to the arrest and indictment of any of the robbers.

Authorities have described all the suspects as black, wearing hooded sweatshirts and construction helmets to obscure their identities. One wore a Philadelphia Eagles construction helmet and another wore an orange helmet, Kearns said.

One was heavyset and balding. Two wearing green and blue shirts were headed toward the Liberty Village Premium Outlets commuter lot.

The suspects were believed to be traveling toward Route 12 West in two separate vehicles -- a white Chrysler 300 and black Audi A5 -- with Pennsylvania plates.